Speaking only generally regarding the broad types or categories of pipe sealing gaskets which may be used, one option is to simply provide a full face or ring type elastomeric gasket. However, as the applications become more demanding in terms of materials, pressures and temperatures, the gasket constructions become more sophisticated in performance and complex in construction. One step in trying to tailor the gasket construction to the particular sealing application is to create a gasket assembly which allows one to select different materials for the different component parts of that gasket assembly.
Sealing/isolating gasket systems are used when electrical isolation and corrosion control are required on pipes handling gas, natural gas, oil and other hydrocarbon-based medias. These fluid materials are “transported” from one point to another by flowing through adjoining pipe sections. These adjoining pipe sections include end flanges which are securely joined together, typically being bolted together. These pipe end flanges may be generally circular or other suitable shapes. In order to provide the referenced electrical isolation and corrosion control, one approach is to use what is referred to in this industry as an isolation gasket. This isolation gasket is positioned between the adjacent and connected flanges of two joined pipe sections. The type of gasket being described is constructed and arranged for what are best described as critical or extreme applications, including for example the handling of fluid materials which are at an elevated temperature, up to approximately 392 degrees F. (200 degrees C.). The specifications for the type of referenced pipe flanges include, for example, flat face, raised face and ring type joint flanges. These range in NPS size from 0.50 inches to 96.0 inches and greater. Other rating information for these types of gaskets include pressure ratings of ANSI 150-2500# and API 2-10K.
Isolation gaskets of the general type being described herein include a retainer, often using a fiberglass-like material, and an elastomeric or polymeric seal element which is received within a groove which is formed or machined into a surface of the retainer. One consideration is how best to capture the seal element in the groove. While a bonding agent or bonding material might be used, this approach requires a certain amount of time in order for that agent or material to set up and fully cure. This time delay slows the overall assembly process and there is a potential for the seal element which is being bonded in place to shift or move before the agent or material is fully cured. Another concern with this approach using a bonding agent or bonding material is that the seal element is securely locked in that groove and this prevents any type of easy replacement or exchange of that seal element in the event of repair or damage or in the event a different type or style of seal element would be desired. Once bonded in position, removal of that seal element requires some degree of groove clean up and thus a further time delay, particularly when the retainer is to be reused.
Disclosed herein are three isolation gasket constructions. Each of the first two isolation gasket constructions, as described herein, include certain structural characteristics which are seen as beneficial in terms of their resultant performance for certain pipe sealing applications or tasks. The third isolation gasket construction which is disclosed herein focuses on creating a novel and unobvious structural combination of features of each of the first two isolation gasket constructions which provide or contribute to those beneficial attributes.
The first type of isolation gasket which is disclosed herein is a gasket which is constructed with an approximate 0.125 inch thick laminate core with a corresponding deformation-based annular seal element seated in an annular groove in each face of the laminate core. The second type of isolation gasket disclosed herein is a gasket which has a thickness of approximately 0.250 inches-0.305 inches and is constructed and arranged with a steel core faced with a non-metal material. The preferred facing material is a synthetic material such as fiberglass. Spaced apart from the defined bore on each face is a seal element (preferably Teflon®) which is captured within an annular groove and is spring energized by a stainless steel spring.
Each of these isolation gaskets, referring now to the two types described above, has a construction resulting in certain design properties which are preferable or advantageous for certain applications or tasks, but which may be considered to be less than optimal for other applications or tasks which still require some degree of sealing and electrical isolation by using gaskets of this type. For example, the first style of isolation gasket, the one with the thinner laminate core, may not be considered quite as reliable as the second style of isolation gasket, in terms of high pressure applications. Since the laminate layers of these types of gaskets are constructed and arranged with a groove for receipt of the seal element, the thinner laminate limits the cross-sectional size of the annular seal element which may be used. With regard to the second style of isolation gasket, this style is generally regarded as capable of effective sealing at higher pressures as compared to the first style. Again, this is due to the nature of the seal element which may be utilized. However, with the second style of isolation gasket, the presence of a steel core may not allow optimal electrical isolation as it introduces metal into the electrical isolation equation. There are also further issues with regard to the use of a glass reinforced epoxy (GRE) laminate material which is regarded as having certain issues as its thickness increases.
In some of the gasket constructions which are disclosed herein, including variations and alternative embodiments, the seal elements are captured within their corresponding groove within the retainer based on the contours, shapes and geometries of those retainer grooves and of the specific seal elements. The seal elements are retained and captured within their corresponding grooves without the use of a bonding agent or bonding material, such as glue or adhesive, being applied on the key contact surfaces.